Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
  • C07D201/02—Preparation of lactams
  • C07D201/08—Preparation of lactams from carboxylic acids or derivatives thereof, e.g. hydroxy carboxylic acids, lactones or nitriles
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
  • C07D201/16—Separation or purification

Definitions

• the present invention relates to a process for treating lactams. It relates more particularly to a process making it possible to modify the chemical nature of the impurities contained in a medium containing lactams either to transform them into non-annoying compounds or into extractable compounds in subsequent purification operations.
• Lactams and in particular ⁇ -caprolactam a monomer for the preparation of polycaproamide (PA6) are prepared according to several synthetic processes.
• the most industrially used process implements a Beckmann rearrangement reaction of the cyclohexanone oxime with sulfuric acid or oleum, followed by neutralization of the medium by ammonia, then separation and of lactam purification.
• Another proposed method for synthesizing lactam consists in carrying out a cyclizing hydrolysis of an aminoalkylnitrile such as 6-aminocapronitrile for the preparation of ⁇ -caprolactam.
• This reaction can be carried out in the presence or absence of a catalyst, in the liquid or vapor phase. This reaction releases ammonia.
• This latter process is described in numerous patents. By way of example, there may be mentioned US Pat. Nos. 2,357,484, US 2,301,964, FR 2,029,540.
• aminocapronitrile is obtained by hemihydrogenation of adiponitrile by known methods and described in particular in patents DE 836 938; DE 848 654 or US 5 151 543.
• the main use of the lactams produced is the manufacture of polymers or copolymers and more particularly of polyamides or copolyamides intended to be shaped for the production of yarns, fibers, moldings or films, the purity of the lactams must comply with precise and drastic specifications.
• UV absorbance of an aqueous solution of caprolactam represented by a UV index.
• This index is determined by measuring the absorbance of an aqueous solution of caprolactam (50% by weight) at the wavelength of 290 in a cell 1 cm wide.
• a low UV index it is known, in particular to subject the lactam to hydrogenation in the presence of catalyst.
• German patent 1 253 716 describes the hydrogenation of caprolactam obtained by the Beckmann rearrangement process in the presence of hydrogenation catalyst in suspension.
• patent DE 1 004 616 and East German 75 083 describes a process for the hydrogenation of caprolactam after treatment with active carbon and ion exchange resins.
• US Patent 5,496,941 describes a process for purifying the lactam obtained by cyclizing hydrolysis of an aminonitrile. This process includes a step of hydrogenating the lactam in the presence of a hydrogenation catalyst.
• a solvent such as water or an alcohol is preferably present.
• the hydrogenation step is carried out on the isolated lactam and separated from the cyclizing hydrolysis reaction medium.
• this process requires the separation of more volatile and less volatile compounds than caprolactam from the cyclizing hydrolysis medium. This separation therefore requires the elimination of the ammonia produced and the distillation of the caprolactam.
• the subject of the invention is a process for treating a liquid medium comprising at least one lactam, in particular for reducing the UV index of the lactam, consisting in subjecting said medium to hydrogenation in the presence of a catalyst d hydrogenation.
• the process is characterized by the presence of ammonia dissolved in said medium.
• ammonia makes it possible to significantly increase the cycle time of the hydrogenation catalyst.
• the temperature for carrying out the hydrogenation will be carried out at a temperature which makes it possible to have a hydrogenation kinetics compatible with industrial exploitation, but the lowest possible.
• this temperature is less than 150 ° C., in particular when the lactam is ⁇ -caprolactam.
• the temperature is between 50 ° C and 150 ° C, preferably between 70 ° C and 130 ° C.
• the concentration of ammonia in the medium can vary in large proportions, but is advantageously greater than 10 g / l, preferably between 50 g / l and 200 g / l.
• the medium containing the lactam comprises, according to a characteristic of the invention, a solvent chosen, for example, from alcohols comprising from 1 to 3 carbon atoms. However, the preferred solvents of the invention are water and water / alcohol mixtures.
• the treatment process of the invention is carried out in the presence of a hydrogenation catalyst.
• This catalyst can be suspended in the medium, or present in the form of a fixed bed or fluidized bed deposited in a tubular reactor.
• the catalyst can be a bulk or supported catalyst.
• the preferred catalysts of the invention are those derived from one or more metals chosen from the group comprising iron, nickel, cobalt, ruthenium, rhodium, palladium, osmium, iridium, platinum.
• catalyst support it is possible to use, for example, activated carbon, aluminas, silicas, titanium oxides, rare earth oxides such as lanthanum or cerium oxides, zirconium or zinc oxides. It is also possible to use a mixture of these oxides or mixed oxides. Can also be used as catalyst support silicates or phosphates of magnesium, aluminum, boron.
• the concentration of catalytic element expressed by weight of metal is advantageously between 0.01 and 80% of the total weight of the catalyst, preferably from 0.1 to 50% by weight.
• the catalysts can comprise additives improving the catalytic effect such as for example zirconium, manganese, copper, chromium, titanium, molybdenum, tungsten, iron or zinc.
• doping elements usually represent by weight relative to the catalytically active metal from 0 to 15% and preferably from 0.1 to 10%.
• this hydrogen treatment makes it possible in particular to reduce the UV index of caprolactam.
• the presence of dissolved ammonia makes it possible to obtain a low UV index even after a long period of continuous operation of the operation, that is to say to process a large quantity of lactam without having to replace or regenerate the catalyst present in the reactor, or by minimizing the consumption of catalyst consumed per kilogram of lactam treated.
• the invention applies to the treatment of lactams of different origins such as those obtained by the Beckmann arrangement reaction, the lactams obtained by depolymerization of polyamide or else the lactams obtained by cyclizing hydrolysis of an aminonitile, for example.
• the invention applies more particularly to the treatment of lactam solutions obtained by hydrolysis of an aminonitrile either in the vapor phase or in the liquid phase.
• the process of the invention applies more particularly, in the hydrogenation steps described in the processes for purifying caprolactam obtained by cyclizing hydrolysis of an aminonitrile in the vapor phase or in the liquid phase described in US Pat. No. 5,496 941 and patent application WO 98/05636.
• Another subject of the invention consists of a process for purifying lactam obtained by cyclizing hydrolysis of an aminonitrile in the vapor phase and more particularly a process for purifying ⁇ -caprolactam obtained by cyclizing hydrolysis in the vapor phase of 6-aminocapronitrile.
• This process consists of:
• the hydrogenation treatment carried out directly on the reaction medium resulting from the cyclizing hydrolysis makes it possible to use the ammonia produced to carry out this hydrogenation under satisfactory economic conditions in particular with a cycle time of the catalyst compatible with economic industrial exploitation . If necessary, it is possible to adjust the ammonia concentration either by adding ammonia, or partial evaporation of the ammonia produced by the hydrolysis reaction. In addition, it also has the effect of reducing the degradation of the UV index which is observed during the separation of the light fractions from the reaction medium, in particular during the distillation of ammonia and optionally of the water or solvent present in the middle.
• the lactam recovered after the hydrogenation treatment and optionally the separation of the ammonia can be subjected to various purification steps known and described in numerous patents such as, for example, US Pat. No. 5,496,941, WO 98/05636, ..
• the possible treatments are oxidation, distillation in an acidic or basic medium, liquid / liquid extraction, treatment on ion exchange resins, crystallization, for example.
• the UV index of this measured solution is 24 to 290 nm.
• the UV index of the solution leaving the hydrogenation step is periodically checked to determine the efficiency of the hydrogenation and therefore the activity of the catalyst.
• Example 1 is repeated but using as a solution of caprolactam in water to which ammonia has been added to obtain a solution containing 90 g / l of ammonia and 61% of caprolactam.
• the caprolactam solution before treatment has a UV index measured at 290 nm of 1.6.
• the caprolactam solution treated by hydrogenation according to the conditions of Example 1 is the reaction medium resulting from the reaction of 6 aminocapronitrile with water. This medium underwent rapid cooling to a temperature of 80 ° C. at the outlet of the reactor to avoid polycondensation of the caprolactam.
• the medium contains 90 g / l of ammonia produced by the reaction. This medium has a UV index at 290 nm of 1.8.
• the medium is directly subjected to hydrogenation according to the conditions of Example 1. The results obtained are given in the table below.
• aminocapronitrile which has not been transformed into caprolactam is completely hydrogenated to hexamethylene diamine, even after 192 hours of operation of the hydrogenation catalyst.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Other In-Based Heterocyclic Compounds (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
• Cephalosporin Compounds (AREA)
• Polyamides (AREA)
• Catalysts (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Nitrogen Condensed Heterocyclic Rings (AREA)
• Pyrrole Compounds (AREA)
• Hydrogenated Pyridines (AREA)

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• 1998
  • 1998-11-19 FR FR9814735A patent/FR2786180B1/fr not_active Expired - Fee Related
• 1999
  • 1999-11-18 MX MXPA01004941A patent/MXPA01004941A/es unknown
  • 1999-11-18 CA CA002351655A patent/CA2351655A1/fr not_active Abandoned
  • 1999-11-18 ES ES99956070T patent/ES2193760T3/es not_active Expired - Lifetime
  • 1999-11-18 CN CN99813466A patent/CN1126736C/zh not_active Expired - Fee Related
  • 1999-11-18 TW TW088120158A patent/TW467895B/zh not_active IP Right Cessation
  • 1999-11-18 BR BR9915501-0A patent/BR9915501A/pt not_active IP Right Cessation
  • 1999-11-18 AT AT99956070T patent/ATE236876T1/de not_active IP Right Cessation
  • 1999-11-18 JP JP2000583859A patent/JP3958935B2/ja not_active Expired - Fee Related
  • 1999-11-18 DE DE69906784T patent/DE69906784T2/de not_active Expired - Lifetime
  • 1999-11-18 WO PCT/FR1999/002823 patent/WO2000031031A1/fr active Application Filing
  • 1999-11-18 RU RU2001116567/04A patent/RU2216538C2/ru not_active IP Right Cessation
  • 1999-11-18 SK SK676-2001A patent/SK6762001A3/sk unknown
  • 1999-11-18 EP EP99956070A patent/EP1131287B1/de not_active Expired - Lifetime
  • 1999-11-18 UA UA2001053276A patent/UA67806C2/uk unknown
  • 1999-11-18 CZ CZ20011738A patent/CZ20011738A3/cs unknown
  • 1999-11-18 PL PL99348364A patent/PL348364A1/xx not_active Application Discontinuation
  • 1999-11-18 KR KR10-2001-7006320A patent/KR100424123B1/ko not_active IP Right Cessation
• 2001
  • 2001-05-21 US US09/860,437 patent/US6579979B2/en not_active Expired - Fee Related

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